These days, it's highly probable one can get help via internet forums using a telephone.

The other way is to load reference info onto a phone as a resource, just in case.

Here's some info paraphrased from a Tom Cutter doc. I hope it might be helpful to someone, in the unfortunate instance where the info is needed.

Troubleshooting BMW-fitted electronic ignition Airheads 1981-1996

* Disconnect battery neg from battery before removal of the front engine cover.

Disconnect bean can 3-pin connector below diode board. It has a wire bail that is a PITA to remove.
Use a hooked pick to pull one end of the clip and the connector will release. Handle the connector carefully, old ones often crumble in your hands. If that starts to happen, MARK each of the three wires as to position, and make a note of the marks. You can insulate the three wires and connect them individually as a makeshift.

Position a wire or straightened, unpainted paper clip into the centre female terminal on the harness side of the connection.

Remove ONE spark plug. Reconnect the plug to the HT cable, firmly ground the spark plug in a location where it cannot fall off, has good ground and where you can clearly see the spark. Best in low light.

COIL and WIRING TEST: Flick kill switch on and off as you watch the spark plug. Got ONE spark each time? The coils are OK, stop suspecting them.

BEAN CAN TEST: Scratch the paper clip across the alternator housing (unpainted aluminium=good ground) like striking a match, while looking at the spark plug:

IF you see spark as you scratch the paper clip across ground, the BEAN CAN is bad - probably failed HES. Repair or replace bean can. BMW doesn't sell them anymore.

If you DO NOT SEE spark, most likely culprit is the Ignition Control Unit under the tank. (By process of elimination.)

If you remove or replace the ICU, clean off the mount, remove and replace the old heat sink compound. Don’t install without heat sink compound. Replace it every few years. More if you ride a lot in hot conditions.

• Don’t forget to disconnect the battery before reinstalling the front cover.